All Caches
* Add default options to initializer that will be sent to all read, write, fetch, exist?, increment, and decrement
* Add support for the :expires_in option to fetch and write for all caches. Cache entries are stored with the create timestamp and a ttl so that expiration can be handled independently of the implementation.
* Add support for a :namespace option. This can be used to set a global prefix for cache entries.
* Deprecate expand_cache_key on ActiveSupport::Cache and move it to ActionController::Caching and ActionDispatch::Http::Cache since the logic in the method used some Rails specific environment variables and was only used by ActionPack classes. Not very DRY but there didn't seem to be a good shared spot and ActiveSupport really shouldn't be Rails specific.
* Add support for :race_condition_ttl to fetch. This setting can prevent race conditions on fetch calls where several processes try to regenerate a recently expired entry at once.
* Add support for :compress option to fetch and write which will compress any data over a configurable threshold.
* Nil values can now be stored in the cache and are distinct from cache misses for fetch.
* Easier API to create new implementations. Just need to implement the methods read_entry, write_entry, and delete_entry instead of overwriting existing methods.
* Since all cache implementations support storing objects, update the docs to state that ActiveCache::Cache::Store implementations should store objects. Keys, however, must be strings since some implementations require that.
* Increase test coverage.
* Document methods which are provided as convenience but which may not be universally available.
MemoryStore
* MemoryStore can now safely be used as the cache for single server sites.
* Make thread safe so that the default cache implementation used by Rails is thread safe. The overhead is minimal and it is still the fastest store available.
* Provide :size initialization option indicating the maximum size of the cache in memory (defaults to 32Mb).
* Add prune logic that removes the least recently used cache entries to keep the cache size from exceeding the max.
* Deprecated SynchronizedMemoryStore since it isn't needed anymore.
FileStore
* Escape key values so they will work as file names on all file systems, be consistent, and case sensitive
* Use a hash algorithm to segment the cache into sub directories so that a large cache doesn't exceed file system limits.
* FileStore can be slow so implement the LocalCache strategy to cache reads for the duration of a request.
* Add cleanup method to keep the disk from filling up with expired entries.
* Fix increment and decrement to use file system locks so they are consistent between processes.
MemCacheStore
* Support all keys. Previously keys with spaces in them would fail
* Deprecate CompressedMemCacheStore since it isn't needed anymore (use :compress => true)
[#4452 state:committed]
Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

… to ActiveSupport::Cache::*. If you're explicitly referring to a store, like ActionController::Caching::Fragments::MemoryStore, you need to update that reference with ActiveSupport::Cache::MemoryStore [DHH] Deprecated ActionController::Base.fragment_cache_store for ActionController::Base.cache_store [DHH] All fragment cache keys are now by default prefixed with the 'views/' namespace [DHH] Added ActiveRecord::Base.cache_key to make it easier to cache Active Records in combination with the new ActiveSupport::Cache::* libraries [DHH] Added ActiveSupport::Gzip.decompress/compress(source) as an easy wrapper for Zlib [Tobias Luetke] Included MemCache-Client to make the improved ActiveSupport::Cache::MemCacheStore work out of the box [Bob Cottrell, Eric Hodel] Added config.cache_store to environment options to control the default cache store (default is FileStore if tmp/cache is present, otherwise MemoryStore is used) [DHH]
git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@8546 5ecf4fe2-1ee6-0310-87b1-e25e094e27de